Use the PHP array_intersect_key() function to get the intersection

When developing using PHP, it often involves processing arrays. Among them, taking the intersection of two arrays is a common task. PHP provides a very convenient function array_intersect_key() to handle this problem.

The array_intersect_key() function is to retain only elements with the same key name in two or more arrays and return the result array. Simply put, it takes the intersection of two arrays, but only compares their keys instead of their values.

The parameters of this function are two or more arrays that need to be compared, which can be one or more. The following is the syntax of this function:

array_intersect_key(array1, array2 [, array3...])

Among them, array1 is the first array to be compared, array2 is the second array, and array3 can be more arrays. If array3 and more arrays are not specified, only the first two arrays are compared by default.

The following is a simple example demonstrating how to use the array_intersect_key() function:

$array1 = array('a'=>'apple', 'b'=>'banana', 'c'=>'cherry');
$array2 = array('a'=>'orange', 'c'=>'cherry', 'd'=>'dates');
$result = array_intersect_key($array1, $array2);
print_r($result);

In the above example, we define two arrays $array1 and $array2, which contain Some key-value pairs. Then, we called the array_intersect_key() function, passing $array1 and $array2 as parameters. This function returns a result array containing elements with the same key in $array1 and $array2. Finally, use the print_r() function to output the result array.

Run the above example, you will get the following output:

Array
(
    [a] => apple
    [c] => cherry
)

As you can see, the function returns a new array, which only contains a and c in $array1 and $array2 elements with the same key name.

It should be noted that this function compares key names rather than key values. If the two arrays have the same key name but different values, then the function will use the value in array 1 as the value in the result array.

When using the array_intersect_key() function, you also need to pay attention to the following points:

1. This function only compares key names and not key values. If you need to compare key values, use the array_intersect() function.
2. If two or more arrays have the same key name but different key values, the result returned by this function contains the value corresponding to the key in the first array.
3. If no identical key name is found, the function returns an empty array.

To sum up, the array_intersect_key() function is a very practical function that can easily obtain the intersection of two or more arrays and will be used very frequently in PHP development. .

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